Common search space (css) for paging of nb-iot devices

ABSTRACT

A method performed by a user equipment (UE) in idle mode, for determining common search space (CSS) for NB-IoT paging is disclosed. The method comprises determining a set of periodic subframes as a Paging Occasion (PO) subframe pattern. The method further comprises monitoring a starting subframe of paging CSS for a Radio Network Temporary Identifier (RNTI). The starting subframe of paging CSS is determined as follows: a first subframe (SF0) defined by the Paging Occasion subframe pattern, is used when SF0 is determined to be a valid downlink subframe. A next valid downlink subframe after SF0 is used when SF0 is determined to be an invalid downlink subframe.

TECHNICAL FIELD

This disclosure relates, in general, to wireless communications, andmore specifically, to determining common search space (CSS for paging ofNarrowband Internet of Things (NB-IoT) systems and devices.

BACKGROUND

Narrow Band Internet of Things (NB-IoT) is a narrowband (180 KHzbandwidth) system being developed for the cellular internet of things by3GPP. The system is based on LTE systems and addresses optimized networkarchitecture and improved indoor coverage for a massive number ofdevices with any one or more of the following characteristics:

-   -   low throughput devices (e.g., 2Kbps)    -   low delay sensitivity (e.g., ˜10 seconds)    -   ultra-low device cost (e.g., below 5 dollars)    -   low device power consumption (e.g., battery life of 10 years)

It is envisioned that each cell (e.g., ˜1 km²) in this system will servethousands (e.g., ˜50 thousand) of wireless devices such as sensors,meters, actuators, etc. It is imperative that this system can providegood coverage for its devices, which often are located deep indoors e.g.underground in basements, or even built into walls of a building andwith limited or no possibility for battery charging. Although manydifferent types of devices are envisioned, for the sake of simplicitythey will be referred to as wireless devices (WDs) or user equipments(UEs) throughout this document.

In order to make it possible to deploy NB-IoT using only one refarmedGSM carrier and support lower manufacturing costs for NB-IoT UEs, thebandwidth has been reduced to one physical resource block (PRB) of size180 KHz divided into several subcarriers.

For frequency division duplex or FDD (i.e. the transmitter and thereceiver operate at different carrier frequencies), only half-duplexmode needs to be supported in the UE. The lower complexity of thedevices (e.g., only one transmission/receiver chain) means that somerepetition might be needed also in normal coverage. Further, toalleviate UE complexity, the working assumption is to havecross-subframe scheduling. That is, a transmission is first scheduled onan Enhanced Physical DL Control Channel (E-PDCCH, also known asNB-PDCCH) and then the first transmission of the actual data on thePhysical DL Shared Channel (PDSCH) is carried out after the finaltransmission of the NB-PDCCH. Similarly, for uplink (UL) datatransmission, information about resources scheduled by the network andneeded by the UE for UL transmission is first conveyed on the NB-PDCCH,and then the first transmission of the actual data by the UE on thePhysical UL Shared Channel (PUSCH) is carried out after the finaltransmission of the NB-PDCCH. In other words, for both cases above,there is no simultaneous reception of control channel andreception/transmission of data channel from the UE's perspective.

The following text is an excerpt from section 7 of 3GPP TS 36.304, theentirety of which is herein incorporated by reference:

-   -   7. Paging    -   7.1 Discontinuous Reception for paging    -   The UE may use Discontinuous Reception (DRX) in idle mode in        order to reduce power consumption. One Paging Occasion (PO) is a        subframe where there may be P-RNTI transmitted on PDCCH        addressing the paging message. One Paging Frame (PF) is one        Radio Frame, which may contain one or multiple Paging        Occasion(s). When DRX is used the UE needs only to monitor one        PO per DRX cycle.    -   PF and PO is determined by following formulae using the DRX        parameters provided in System Information:    -   PF is given by following equation:

SFN mod T=(T div N)*(UE_ID mod N)

-   -   Index i_s pointing to PO from subframe pattern defined below        will be derived from following calculation:

i_s=floor(UE_ID/N)mod Ns

-   -   System Information DRX parameters stored in the UE shall be        updated locally in the UE whenever the DRX parameter values are        changed in SI. If the UE has no IMSI, for instance when making        an emergency call without USIM, the UE shall use as default        identity UE_ID−0 in the PF and i_s formulas above.    -   The following Parameters are used for the calculation of the PF        and i_s:        -   T: DRX cycle of the UE. T is determined by the shortest of            the UE specific DRX value, if allocated by upper layers, and            a default DRX value broadcast in system information. If UE            specific DRX is not configured by upper layers, the default            value is applied.        -   nB: 4T, 2T, T, T/2, T/4, T/8, T/16, T/32.        -   N: min(T,nB)        -   Ns: max(1,nB/T)        -   UE_ID: IMSI mod 1024.    -   IMSI is given as sequence of digits of type Integer (0 . . . 9),        IMSI shall in the formulae above be interpreted as a decimal        integer number, where the first digit given in the sequence        represents the highest order digit.    -   For example:

IMSI=12(digit1=1, digit2=2)

-   -   In the calculations, this shall be interpreted as the decimal        integer “12”, not “1×16+2=18”.    -   7.2 Subframe Patterns    -   FDD:

TABLE 0-1 PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 9 N/A N/A N/A 2 4 9 N/A N/A 4 0 4 5 9

-   -   TDD (all UL/DL configurations):

TABLE 0-2 PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 0 N/A N/A N/A 2 0 5 N/A N/A 4 0 1 5 6

SUMMARY

As can be seen from the excerpt above, the current approach providesinadequate paging opportunities for NB-IoT UEs (e.g., zero or limitednumber of paging occasions). Thus, this provides limited or inadequateopportunities for NB-IoT UEs to adequately communicate.

In this disclosure, we propose methods and apparatuses to address theseissues by determining paging occasion (PO), paging frame (PF), andcommon search space (CSS) for NB-IoT UE. This provides more adequateopportunities for NB-IoT devices to communicate.

Various embodiments are disclosed herein for monitoring, aligning,modifying, and/or assigning paging occasions and/or paging frames forNB-IoT UEs. According to particular embodiments methods and apparatusesare disclosed for use when subframes are occupied by other broadcastchannels or signals. According to additional embodiments, methods andapparatuses are disclosed for inband operation. According to additionalembodiments, methods and apparatuses are disclosed for standalone orguard band operation. According to additional embodiments, methods andapparatuses are disclosed for determining paging CSS using validsubframe pattern without changing PO subframe pattern. The variousmethods described herein may be performed by a wireless device, a UE, anetwork node, or some suitable combination of apparatuses.

A method performed by a wireless device is disclosed. The methodcomprises determining a set of periodic subframes as a Paging Occasion(PO) subframe pattern and monitoring a starting subframe of paging CSSfor a Radio Network Temporary Identifier (RNTI). The starting subframeof paging CSS is determined as follows: (i) a first subframe (SF0),defined by the Paging Occasion subframe pattern, is used when SF0 isdetermined to be a valid downlink subframe; and (ii) a next validdownlink subframe after SF0 is used when SF0 is determined to be aninvalid downlink subframe.

In some embodiments, the subframe is determined to be a valid downlinksubframe if the subframe is indicated as a valid downlink subframe in aNarrowband System Information Block 1 (NB-SIB1) and the subframe doesnot include any of the following: NPSS, NSSS, NPBCH, and NB-SIB1.

Also disclosed is a wireless device. The wireless device comprisesprocessing circuitry configured to determine a set of periodic subframesas a Paging Occasion (PO) subframe pattern and monitor a startingsubframe of paging CSS for a Radio Network Temporary Identifier (RNTI).The starting subframe of paging CSS is determined as follows: (i) afirst subframe (SF0), defined by the Paging Occasion subframe pattern,is used when SF0 is determined to be a valid downlink subframe; and (ii)a next valid downlink subframe after SF0 is used when SF0 is determinedto be an invalid downlink subframe. The wireless device may furthercomprise power supply circuitry configured to supply power to thewireless device.

In some embodiments, the subframe is determined to be a valid downlinksubframe if the subframe is indicated as a valid downlink subframe in aNarrowband System Information Block 1 (NB-SIB1) and the subframe doesnot include any of the following: NPSS, NSSS, NPBCH, and NB-SIB1.

A user equipment, UE, for determining common search space (CSS) forNB-IoT paging while operating in idle mode is also disclosed. The UEcomprises an antenna configured to send and receive wireless signals.The UE further comprises radio front-end circuitry connected to theantenna and to processing circuitry, and configured to condition signalscommunicated between the antenna and the processing circuitry. Theprocessing circuitry is configured to determine a set of periodicsubframes as a Paging Occasion (PO) subframe pattern and monitor astarting subframe of paging CSS for a Radio Network Temporary Identifier(RNTI). The starting subframe of paging CSS is determined as follows:(i) a first subframe (SF0), defined by the Paging Occasion subframepattern, is used when SF0 is determined to be a valid downlink subframe;and (ii) a next valid downlink subframe after SF0 is used when SF0 isdetermined to be an invalid downlink subframe. The user equipmentfurther comprises an input interface connected to the processingcircuitry and configured to allow input of information into the UE to beprocessed by the processing circuitry, and an output interface connectedto the processing circuitry and configured to output information fromthe UE that has been processed by the processing circuitry. Yet further,the user equipment comprises a battery connected to the processingcircuitry and configured to supply power to the UE.

In some embodiments, the subframe is determined to be a valid downlinksubframe if the subframe is indicated as a valid downlink subframe in aNarrowband System Information Block 1 (NB-SIB1) and the subframe doesnot include any of the following: NPSS, NSSS, NPBCH, and NB-SIB1.

A method performed by a network node is also disclosed. The methodcomprises determining a set of periodic subframes as a Paging Occasion(PO) subframe pattern and transmitting a paging message to a UserEquipment (UE), the paging message beginning with a starting subframe ofpaging CSS. The starting subframe of paging CSS is determined asfollows: (i) a first subframe (SF0), defined by the Paging Occasionsubframe pattern, is used when SF0 is determined to be a valid downlinksubframe; and (ii) a next valid downlink subframe after SF0 is used whenSF0 is determined to be an invalid downlink subframe.

In some embodiments, the network node indicates a subframe as a validdownlink subframe in a Narrowband System Information Block 1 (NB-SIB1).The network node determines the subframe is a valid downlink subframe ifthe subframe does not contain any of the following: NPSS, NSSS, NPBCH,and NB-SIB 1.

A network node for determining common search space (CSS) for NB-IoTpaging is also disclosed. The network node includes processing circuitryconfigured to determine a set of periodic subframes as a Paging Occasion(PO) subframe pattern and transmit a paging message to a User Equipment(UE), the paging message beginning with a starting subframe of pagingCSS. The starting subframe of paging CSS is determined as follows: (i) afirst subframe (SF0), defined by the Paging Occasion subframe pattern,is used when SF0 is determined to be a valid downlink subframe; and (ii)a next valid downlink subframe after SF0 is used when SF0 is determinedto be an invalid downlink subframe.

In some embodiments, the network node indicates a subframe as a validdownlink subframe in a Narrowband System Information Block 1 (NB-SIB1).The network node determines the subframe is a valid downlink subframe ifthe subframe does not contain any of the following: NPSS, NSSS, NPBCH,and NB-SIB 1.

Certain embodiments of the present disclosure may provide one or moretechnical advantages. For example, some embodiments may advantageouslyprovide more adequate opportunities for NB-IoT devices to communicate.Some embodiments allow the NB-IoT transmission to flexibly adapt to thevalid downlink subframe pattern. Some embodiments advantageously providethe same paging mechanism for NB-IoT devices regardless of operationmode, including inband operation, standalone operation, and guard bandoperation. Furthermore, some embodiments may prevent collisions offrames sent via paging. Other advantages may be readily available to onehaving skill in the art. Certain embodiments may have none, some, or allof the recited advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram for an example method performed by auser equipment in accordance with certain embodiments of the presentdisclosure.

FIG. 2 is a process flow diagram for an example method performed by anetwork node in accordance with certain embodiments of the presentdisclosure.

FIG. 3 is a schematic diagram of an example wireless communicationnetwork in accordance with certain embodiments of the presentdisclosure.

FIG. 4 is a schematic diagram of an example user equipment in accordancewith certain embodiments of the present disclosure.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described morefully hereinafter with reference to the accompanying drawings. Otherembodiments, however, are contained within the scope of this disclosureand the invention should not be construed as limited to only theembodiments set forth herein; rather, these embodiments are provided byway of example to convey the scope of the inventive concept to thoseskilled in the art. Like numbers refer to like elements throughout thedescription.

1.1 Subframes Occupied by Other Broadcast Channels/Signals

According to particular embodiments, subframes occupied by otherbroadcast channels or signals may interfere with paging messages. Pagingtransmission is associated with a paging Radio Network TemporaryIdentifier (P-RNTI). It can be sent via either of two variations:

-   -   (a) NB-IoT Physical Downlink Control Channel (NPDCCH) without        NB-IoT Physical Downlink Shared Channel (NPDSCH). This variant        could be used for notify about System Information (SI) updates.        In this case, the downlink control information (DCI) carried by        NPDCCH may contain a flag which indicates that there is an SI        update without scheduling information of NPDSCH. If NB-IoT UEs        support Earthquake & Tsunami Warning System (ETWS), Cellular        Messaging Alert System (CMAS), Extended Access Barring (EAB), or        various other alerts or messages, the DCI may provide an        indicator for these as well.    -   (b) NPDCCH with the corresponding NPDSCH. This variant could be        used for sending a paging message, where the DCI bits carry        scheduling information of NPDSCH for a paging message.

For NB-IoT operation, subframes {0, 4, 5, 9} are densely occupied byother broadcast channels/signals including, but not limited to thefollowing:

-   -   NPBCH: NPBCH fully occupies the PRB at subframe 0 in every radio        frame;    -   NPSS: NPSS is transmitted in subframe 5 with periodicity of 10        ms. NPSS uses the last 11 OFDM symbols of subframes in which        NPSS occurs for normal CP. That is, NPSS takes subframe 5 in        every radio frame;    -   NSSS: NSSS is transmitted in subframe 9. NSSS uses the last 11        OFDM symbols of subframes in which NSSS occurs for normal CP.        Periodicity of NSSS has been set at 20 ms;    -   NSIB1 (NB-IoT System Information Block): NSIB1 is transmitted in        subframe #4 within each radio frame transmitting NSIB1. The        radio frame occupied by NSIB1 occurs in every other frame in 16        consecutive radio frames, with the cluster 16 radio frame occurs        every {64, 32, 16} radio frames.

As can be seen, these broadcast channels/signals are generallytransmitted on particular subframes according a pattern that is known toboth network nodes and wireless devices operating within the system.Given the densely occupied subframes, there is a need to provide asufficient number of opportunities for sending paging so that thevarious nodes and devices can communicate. Common search space (CSS) forpaging is the key for sending NPDCCH of paging. According to particularembodiments, a UE monitors the CSS for paging for potential pagingtransmission. The potential starting point of CSS for paging is thenaligned with the paging occasion (PO), which may be defined for a givenUE. In order to have sufficient opportunities to page the UEs in thecell, then there needs proper definition of paging frame (PF) and pagingoccasion (PO). After alignment, the UE is then able to send pagingtransmissions.

1.2 Inband Operation

For all operation modes, including multi-PRB operation, the UE receivespaging on the anchor PRB. Other than paging NPDCCH and NPDSCH, severaltypes of broadcast channels and signals may also take place on the samePRB, including NPBCH, NPSS, NSSS, NSIB1, and other SIB transmission.

Additionally, for inband operation, an MBSFN subframe pattern exists andmust be adhered to. This limits the subframes to SF {0, 4, 5, 9} in aradio frame for transmitting NPBCH, NPSS, NSSS, NSIB1, paging startingsubframe.

Thus, compared to legacy LTE, the possible subframes to start paging CSSis very limited:

-   -   Subframe 4 in those radio frames not occupied by NSIB 1;    -   Subframe 9 in those radio frames not occupied by NSSS;

1.2.1 Indication Directly with Absolute Subframe Indices

Subframe 0 and 5 are not available for paging CSS any longer. Accordingto particular embodiments, the paging subframe pattern for FDD may thenbe modified to Table 1.

To provide sufficient opportunities to page NB-IoT UEs, severalmechanisms are considered:

-   -   1. Preserve sufficient number of paging opportunities. For        example, NSSS is transmitted at most in every other radio frame.        This leaves at least subframe 4 in every other radio frame for        paging CSS.    -   2. Define mechanisms to handle collision.        -   a. In one embodiment, if the {PF, PO} resulting from a            legacy PF/PO calculation collides with another broadcast            transmission, then the UE is paged in the next non-colliding            RF with the same PO. For example, if the paging occasion            collides with the NSSS or NSIB1 transmission, the UE is            paged in the next available radio frame not containing NSSS            or NSIB1. In this case, the {PF, PO} may be outside the set            of possible paging opportunities according to PF/PO            calculation. That is,            -   i. If PF with PO=4 collides with a NSSS transmission,                the paging CSS of the UE starts in next SFN: SFN′=SFN+1                (mod 1024) with PO=4, where SFN is according to the PF                calculation: SFN mod T=(T div N)*(UE_ID mod N). Note                that (mod 1024) is necessary to take care of SNR wrap                around.            -   ii. If PF with PO=9 collides with a NSIB1 transmission,                the paging CSS of the UE starts in next SFN: SFN′=SFN+1                (mod 1024) with PO=9, where SFN is according to the PF                calculation: SFN mod T=(T div N)*(UE_ID mod N).        -   b. In another embodiment, if the {PF, PO} resulting from            legacy PF/PO calculation collides with another broadcast            transmission (e.g., NSIB1 or NSSS), then the UE is paged in            the next non-colliding PO available to the UE. The next            non-colliding PO can be in the current calculated PF, or the            subsequent available PF according to PF calculation.

TABLE 1 Paging subframe pattern for FDD (modifications shown withstrikethrough): PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s =2 i_s = 3 1 9 N/A N/A N/A 2 4 9 N/A N/A 4

 N/A 4

 N/A 9 Note that for NB-IoT in TDD system in the future, similar methodscan be used to handle collisions. That is, delay to the nextnon-colliding radio frame of the same PO, or delay to the next availablePO available to the UE.

1.2.2 Indication Indirectly with Valid Subframe Indices

According to other embodiments, additional subframes that are not usedfor paging in legacy LTE operation are made available for paging forNB-IoT. This may be beneficial if paging capacity becomes a bottleneckfor NB-IoT. A parameter indicative of what subframes that are consideredas valid downlink subframes in the cell may already be broadcasted forother purposes throughout the cell. The set of valid DL subframes can besignaled in the form of a bitmap in a system information block. Forexample, the bitmap is [b(0), b(1), . . . , b(p-1)], where b(i)=0indicates subframe i in the period is an invalid DL subframe, whileb(i)=1 indicates subframe i in the period is a valid DL subframe.

If this bitmap parameter indicates that some downlink subframes areconsidered valid subframes, it can be assumed that these subframes willnot be used for MBSFN transmission, and then these subframes can be usedfor paging.

Let the cell-specific valid subframe set be {vsf(0), vsf(1), . . .vsf(m-1)} by taking those b(i)>1 in the bitmap, where m is the totalnumber of valid DL subframes in the period of p subframes, m<=p. Thenthe PO can be defined using one or more of vsf. One example is listedbelow in Table 1-1, assuming there are m>=4 vsf over the time duration pthe vsf is defined over. While existing paging occasion definition isover a radio frame (i.e., 10 subframes, which is equal to 10 ms), thevsf may be defined over a radio frame or other appropriate durations.Typical durations for defining vsf are: (a) p=10, i.e., 10 subframes (=1radio frame); (b) p=40, i.e., 40 subframes (=4 radio frames).

Using the vsf concept in defining PO could avoid collision with thosesubframes which are taken into account in defining the vsf. However,collision with those subframes which are not taken into account indefining the vsf can still happen. For example, subframe #9 may not bedesignated as invalid DL subframe since NSSS does not occupy subframe #9in all radio frames. Thus, paging CSS may still collide with NSSS usingthe vsf concept. Thus there is still the need to define mechanisms tohandle the collision. Mechanisms like those described in the lastsub-section can be used.

TABLE 1-1 Paging subframe pattern defined with valid subframe (vsf)indices: PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 vsf(3) N/A N/A N/A 2 vsf(1) vsf(3) N/A N/A 4 vsf(0) vsf(1) vsf(2)vsf(3)

1.3 Standalone or Guard Band Operation

1.3.1 FDD Standalone or Guard Band Operation

For standalone or guard band operation, the set of subframes occupied byNPBCH, NPSS, NSSS, and NSIB1 are the same as inband operation, asdiscussed above. However, there is no legacy MBSFN transmission.

Hence there are at least two alternatives of handling paging CSS forstandalone and/or guard band operations for FDD system. Two of theseprimary alternatives are discussed below, but it will be appreciatedthat additional embodiments may be used.

-   -   Alternative 1. Do not introduce new subframes for the PO for        paging CSS. In this alternative, the set of subframes possible        to start paging CSS is still {0, 4, 5, 9} for FDD. In this case,        the same mechanisms for defining paging CSS in inband operation        is reused for standalone and guard band operation.    -   Alternative 2. Introduce new subframes for the PO for paging        CSS. In this alternative, new subframe pattern for the PO is        defined. The new subframe pattern can be defined directly by        absolute subframe indices, or indirectly via valid subframe        indices vsf. Below the discussion uses the absolute subframe        indexing way to illustrate.        -   One example is to use a completely new set of subframes,            e.g., subframe {1,2,6,7} instead of subframe {0,4,5,9}.            Correspondingly, the PO table is modified to Table 2.        -   Another example is to replaces a subset of the PO subframes,            but keep the rest of the existing PO subframes. For example,            subframe {0, 5} are replaced by subframe {1, 6},            respectively, but subframe {4, 9} are kept. Correspondingly,            the PO table is modified to Table 3.

TABLE 2 New paging subframe pattern for FDD standalone or guard bandoperation PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 7 N/A N/A N/A 2 2 7 N/A N/A 4 1 2 6 7

TABLE 3 New paging subframe pattern for FDD standalone or guard bandoperation PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 9 N/A N/A N/A 2 4 9 N/A N/A 4

 1 4

 6 9

1.3.2 TDD Standalone or Guard Band Operation

Note that for NB-IoT in TDD system in the future, subframe pattern forPO should be handled as well.

1.3.2.1 TDD Without Broadcasting Valid Subframe Pattern

According to particular embodiments, a TDD system may be used withoutbroadcasting a valid subframe pattern. If no valid subframe pattern isbroadcast, then a new subframe set cannot be defined in place ofsubframe {0,1, 5, 6} if all existing TDD UL/DL configurations areconsidered. This is because subframe {0,1,5,6} is the only set of DL orspecial subframes common to all TDD UL/DL configurations. In this case,only Alternative 1 is possible:

-   -   Alternative 1. Do not introduce new PO for paging CSS. In this        alternative, the set of subframes possible to start paging CSS        is still {0, 1, 5, 6} for TDD. In this case, the same mechanisms        for defining paging CSS in inband operation is reused for        standalone and guard band operation. If the {PF, PO} resulting        from legacy PF/PO calculation collides with the NSSS or NSIB1        transmission, the UE is paged in the next available radio frame        not containing NSSS or NSIB1.

On the other hand, if only a subset of all existing TDD UL/DLconfigurations are considered, more DL or special subframes can beavailable. For example, if only UL/DL configurations 1 and 2 aresupported for NB-IoT, then the set of DL or special subframes common toboth are subframe {0, 1, 4, 5, 6, 9}. In this case, Alternative 1 can beused. In addition, Alternative 2 is also possible. That is,

-   -   Alterative 2. Introduce one or more new PO for paging CSS. For        example, replace a subset of the existing PO subframes with new        PO suframes, but keep the rest of the existing PO subframes. For        example, subframe {0, 5} are replaced by subframe {4, 9},        respectively, but subframe {1, 6} are kept. This is illustrated        by Table 5.

TABLE 4 TDD Uplink-downlink configurations Downlink- Uplink- to-Uplinkdownlink Switch-point Subframe number configuration periodicity 0 1 2 34 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5 msD S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S U U D D DD D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U D

TABLE 5 New paging subframe pattern for TDD standalone or guard bandoperation (changes shown with strikethrough) PO when PO when PO when POwhen Ns i_s = 0 i_s = 1 i_s = 2 i_s = 3 1

 4 N/A N/A N/A 2

 4

 9 N/A N/A 4

 4 1

 9 6

1.3.2.2 TDD with Broadcasting Valid Subframe Pattern

If a valid subframe pattern is broadcast cell-wide, then the vsf can beused to define the subframe pattern for TDD. A table similar to Table1-1 can be constructed for TDD. One example is illustrated below asTable 6.

TABLE 6 Paging subframe pattern defined with valid subframe (vsf)indices: PO when PO when PO when PO when Ns i_s = 0 i_s = 1 i_s = 2 i_s= 3 1 vsf(0) N/A N/A N/A 2 vsf(0) vsf(2) N/A N/A 4 vsf(0) vsf(1) vsf(2)vsf(3)

1.4 Determine Paging CSS Using Valid Subframe Pattern Without ChangingPO Subframe Pattern

According to additional embodiments, the subframes for paging CSS can bedetermined using valid DL subframe pattern without changing the pagingsubframe look-up table. That is, subframe pattern table, Table 0-1 forFDD and Table 0-2 for TDD, are used, the same as in legacy system. Thebenefit of these embodiments is that the total number of pagingopportunities is not reduced.

The starting subframes for paging CSS is determined by the {PF, PO} andvalid DL subframe pattern.

If the subframe sf0 determined by PF and PO is a valid DL subframe, thenthe subframe sf0 is the starting subframe of the paging CSS for this setof {PF, PO}.

If the subframe sf0 determined by PF and PO is NOT a valid DL subframe,then the first valid subframe that come after sf0 is the startingsubframe of the paging CSS for this set of {PF, PO}.

For example,

if {PF, PO} points to a subframe #9 which is occupied by NSSS in thegiven SFN, then the starting subframe of the corresponding paging CSS isdelayed to the next valid DL subframe, for example, subframe #1 of thenext radio frame.

if {PF, PO} points to subframe #9 which is NOT occupied by NSSS in thegiven SFN, then the starting subframe of the corresponding paging CSS isthe subframe #9.

In addition, the paging CSS is defined over valid subframes, where thepaging NPDCCH candidate is only transmitted over valid subframes. Thatis, if a paging NPDCCH repetition runs into an invalid subframe, therepetition is delayed to the next valid subframe.

In one method, the valid subframe pattern VSFa (or invalid subframepattern) is the valid DL pattern broadcast by the eNB via a SIB.

In another method, the invalid subframe pattern for paging is composedof the aggregate of subframes occupied by known broadcastchannel/signal, such as NPBCH/NPSS/NSSS/NSIB1, and not signaled viabroadcast. The valid subframe pattern VSFb is then composed of thosesubframes NOT occupied by the known broadcast channel/signal such asNPBCH/NPSS/NSSS/NSIB1.

In yet another method, the valid subframe pattern is the composite ofVSFa and VSFb. That is, a subframe is deemed a valid subframe only if itis a valid subframe in VSFa and also a valid subframe in VSFb.

According particular embodiments, these solutions may be carried out ina method performed by a user equipment, as illustrated in FIG. 1.

FIG. 1 discloses a method 100, performed by a user equipment (UE),operating in idle mode, for determining common search space (CSS) forNB-IoT paging. The method begins at step 102, when the user equipmentdetermines a set of periodic subframes as a Paging Occasion (PO)subframe pattern. This PO subframe pattern, sometimes referred to as{PF, PO}, may be determined in a variety of manners, including but notlimited to the use of a subframe pattern table. Here PF refers to PagingFrame. Such a table may be defined by existing standards, such assection 7 of 3GPP TS 36.304. According to particular embodiments, thistable may be the table shown in Tables 0-1 and 0-2 above.

Regardless of how the PO subframe pattern is determined, at step 104,the user equipment monitors a starting subframe of paging CSS for aRadio Network Temporary Identifier (RNTI). However, other suitableidentifiers may be used. At step 106, it is determined whether a firstsubframe (SF0), defined by the PO subframe pattern, is a valid downlinksubframe. This determination may be made in a variety of manners.

According to a particular embodiment, the UE determines a subframe is avalid downlink subframe if it is indicated as a valid downlink subframein a Narrowband SIB1 received from a network node. In 3GPP TS 36.331,this NB-SIB1 may be referred to as “SystemInformationBlockTypeI-NB.” TheUE may also determine that a subframe is a valid downlink subframe if itdoes not include any known broadcast channels or signals, including, butnot limited to NPSSS, NSSS, NPBCH, and NB-SIB 1. The UE may alsodetermine that a subframe is a valid downlink subframe if it is includedin a valid subframe pattern. Such a valid subframe pattern may bereceived in a SIB message broadcast by a network node. This may be“downlinkBitmapNB” as referred to in 3GPP TS 36.331 and 36.213. Thevalid subframe pattern may also include subframes not occupied by knownbroadcast channels or broadcast signals. The UE may also determine thata subframe is a valid downlink subframe based on a combination of thesevalid subframe patterns.

According to particular embodiments, the UE may make this determinationof valid downlink subframes based on any of the criteria discussedabove, either alone or in any permissible combination thereof. When itis determined to be a valid subframe, at step 108 SF0 is used as thestarting subframe of paging CSS. When SF0 is not a valid subframe, atstep 110 the next valid downlink subframe after SF0 is used as thestarting subframe of paging CSS. According to particular embodiments,SF0 may be defined to be a starting subframe of Narrowband Physical DataControl Channel (NPDCCH) repetitions. This definition may be included inthe Paging Occasion subframe pattern. According to additionalembodiments, CSS may be defined only over valid downlink subframes.Under these embodiments, when NPDCCH repetition overlaps with an invaliddownlink subframe, the repetition may be delayed until a next validdownlink subframe.

According particular embodiments, the solutions proposed herein may alsobe carried out in a method performed by a network node, as illustratedin FIG. 2.

FIG. 2 discloses a method 200, performed by a network node, fordetermining common search space (CSS) for NB-IoT paging. The methodbegins at step 202, when the network node determines a set of periodicsubframes as a Paging Occasion (PO) subframe pattern. This PO subframepattern, sometimes referred to as {PF, PO}, may be determined in avariety of manners, including but not limited to the use of a subframepattern table. Such a table may be defined by existing standards, suchas section 7 of 3GPP TS 36.304. According to particular embodiments,this table may be the table shown in Tables 0-1 and 0-2 above.

Regardless of how the PO subframe pattern is determined, at step 204,the network node transmits a paging message to a user equipment, thepaging message beginning with a starting subframe of paging CSS. At step206, it is determined whether a first subframe (SF0), defined by the POsubframe pattern, is a valid downlink subframe. This determination maybe made in a variety of manners.

According to a particular embodiment, the network node determines asubframe is a valid downlink subframe if it does not include any knownbroadcast channels or signals, including, but not limited to NPSSS,NSSS, NPBCH, and NB-SIB1. The network may also determine that a subframeis a valid downlink subframe if it is included in a valid subframepattern. An indication of a valid downlink subframe may be provided in aSIB1 transmitted to a user equipment, either in an indication that anindividual subframe is valid, or in the form of a valid subframepattern. The valid subframe pattern may also include subframes notoccupied by known broadcast channels or broadcast signals.

According to particular embodiments, the network node may make thisdetermination of valid downlink subframes based on any of the criteriadiscussed above, either alone or in any permissible combination thereof.When it is determined to be a valid subframe, at step 208 SF0 is used asthe starting subframe of paging CSS. When SF0 is not a valid subframe,at step 210 the next valid downlink subframe after SF0 is used as thestarting subframe of paging CSS. According to particular embodiments,SF0 may be defined to be a starting subframe of Narrowband Physical DataControl Channel (NPDCCH) repetitions. This definition may be included inthe Paging Occasion subframe pattern. According to additionalembodiments, CSS may be defined only over valid downlink subframes.Under these embodiments, when NPDCCH repetition overlaps with an invaliddownlink subframe, the repetition may be delayed until a next validdownlink subframe.

Although the solutions described above may be implemented in anyappropriate type of system using any suitable components, particularembodiments of the described solutions may be implemented in a wirelessnetwork such as the example wireless communication network illustratedin FIG. 3. In the example embodiment of FIG. 3, the wirelesscommunication network provides communication and other types of servicesto one or more user equipments. In the illustrated embodiment, thewireless communication network includes one or more instances of networknodes that facilitate the user equipments' access to and/or use of theservices provided by the wireless communication network. The wirelesscommunication network may further include any additional elementssuitable to support communication between user equipments or between awireless device and another communication device, such as a landlinetelephone.

Network 320 may comprise one or more IP networks, public switchedtelephone networks (PSTNs), packet data networks, optical networks, widearea networks (WANs), local area networks (LANs), wireless local areanetworks (WLANs), wired networks, wireless networks, metropolitan areanetworks, and other networks to enable communication between devices.

The wireless communication network may represent any type ofcommunication, telecommunication, data, cellular, and/or radio networkor other type of system. In particular embodiments, the wirelesscommunication network may be configured to operate according to specificstandards or other types of predefined rules or procedures. Thus,particular embodiments of the wireless communication network mayimplement communication standards, such as Global System for MobileCommunications (GSM), Universal Mobile Telecommunications System (UMTS),Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, or 5Gstandards; wireless local area network (WLAN) standards, such as theIEEE 802.11 standards; and/or any other appropriate wirelesscommunication standard, such as the Worldwide Interoperability forMicrowave Access (WiMax), Bluetooth, and/or ZigBee standards.

FIG. 3 illustrates a wireless network comprising a more detailed view ofnetwork node 300 and user equipment (UE) 310, in accordance with aparticular embodiment. For simplicity, FIG. 3 only depicts network 320,network nodes 300 and 300 a, and UE 310. Network node 300 comprisesprocessor 302, storage 303, interface 301, and antenna 301 a. Similarly,UE 310 comprises processor 312, storage 313, interface 311 and antenna311 a. These components may work together in order to provide networknode and/or user equipment functionality, such as providing wirelessconnections in a wireless network, as well as the embodiments describedabove in FIGS. 1 and 2. In different embodiments, the wireless networkmay comprise any number of wired or wireless networks, network nodes,base stations, controllers, user equipments, relay stations, and/or anyother components that may facilitate or participate in the communicationof data and/or signals whether via wired or wireless connections.

As used herein, “network node” refers to equipment capable, configured,arranged and/or operable to communicate directly or indirectly with auser equipment and/or with other equipment in the wireless communicationnetwork that enable and/or provide wireless access to the userequipment. Examples of network nodes include, but are not limited to,access points (APs), in particular radio access points. A network nodemay represent base stations (BSs), such as radio base stations.Particular examples of radio base stations include Node Bs, and evolvedNode Bs (eNBs). Base stations may be categorized based on the amount ofcoverage they provide (or, stated differently, their transmit powerlevel) and may then also be referred to as femto base stations, picobase stations, micro base stations, or macro base stations. “Networknode” also includes one or more (or all) parts of a distributed radiobase station such as centralized digital units and/or remote radio units(RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remoteradio units may or may not be integrated with an antenna as an antennaintegrated radio. Parts of a distributed radio base stations may also bereferred to as nodes in a distributed antenna system (DAS).

As a particular non-limiting example, a base station may be a relay nodeor a relay donor node controlling a relay.

Yet further examples of network nodes include multi-standard radio (MSR)radio equipment such as MSR BSs, network controllers such as radionetwork controllers (RNCs) or base station controllers (BSCs), basetransceiver stations (BTSs), transmission points, transmission nodes,Multi-cell/multicast Coordination Entities (MCEs), core network nodes(e.g., MSCs, MMEs), O&M nodes, OSS nodes, SON nodes, positioning nodes(e.g., E-SMLCs), and/or MDTs. More generally, however, network nodes mayrepresent any suitable device (or group of devices) capable, configured,arranged, and/or operable to enable and/or provide a user equipmentaccess to the wireless communication network or to provide some serviceto a user equipment that has accessed the wireless communicationnetwork.

As used herein, the term “radio node” is used generically to refer bothto user equipments and network nodes, as each is respectively describedabove.

In FIG. 3, Network node 300 comprises processor 302, storage 303,interface 301, and antenna 301 a. These components are depicted assingle boxes located within a single larger box. In practice however, anetwork node may comprise multiple different physical components thatmake up a single illustrated component (e.g., interface 301 may compriseterminals for coupling wires for a wired connection and a radiotransceiver for a wireless connection). As another example, network node300 may be a virtual network node in which multiple different physicallyseparate components interact to provide the functionality of networknode 300 (e.g., processor 302 may comprise three separate processorslocated in three separate enclosures, where each processor isresponsible for a different function for a particular instance ofnetwork node 300). Similarly, network node 300 may be composed ofmultiple physically separate components (e.g., a NodeB component and aRNC component, a BTS component and a BSC component, etc.), which mayeach have their own respective processor, storage, and interfacecomponents. In certain scenarios in which network node 300 comprisesmultiple separate components (e.g., BTS and BSC components), one or moreof the separate components may be shared among several network nodes.For example, a single RNC may control multiple NodeB's. In such ascenario, each unique NodeB and BSC pair, may be a separate networknode. In some embodiments, network node 300 may be configured to supportmultiple radio access technologies (RATs). In such embodiments, somecomponents may be duplicated (e.g., separate storage 303 for thedifferent RATs) and some components may be reused (e.g., the sameantenna 301 may be shared by the RATs).

Processor 302 may be a combination of one or more of a microprocessor,controller, microcontroller, central processing unit, digital signalprocessor, application specific integrated circuit, field programmablegate array, or any other suitable computing device, resource, orcombination of hardware, software and/or encoded logic operable toprovide, either alone or in conjunction with other network node 200components, such as storage 303, network node 300 functionality. Forexample, processor 302 may execute instructions stored in storage 303.Such functionality may include providing various wireless featuresdiscussed herein to a user equipment, such as UE 310, including any ofthe features or benefits disclosed herein.

Storage 303 may comprise any form of volatile or non-volatile computerreadable memory including, without limitation, persistent storage, solidstate memory, remotely mounted memory, magnetic media, optical media,random access memory (RAM), read-only memory (ROM), removable media, orany other suitable local or remote memory component. Storage 303 maystore any suitable instructions, data or information, including softwareand encoded logic, utilized by network node 300. Storage 303 may be usedto store any calculations made by processor 302 and/or any data receivedvia interface 301.

Network node 300 also comprises interface 301 which may be used in thewired or wireless communication of signalling and/or data betweennetwork node 300, network 320, and/or UE 310. For example, interface 301may perform any formatting, coding, or translating that may be needed toallow network node 300 to send and receive data from network 320 over awired connection. Interface 301 may also include a radio transmitterand/or receiver that may be coupled to or a part of antenna 301 a. Theradio may receive digital data that is to be sent out to other networknodes or UEs via a wireless connection. The radio may convert thedigital data into a radio signal having the appropriate channel andbandwidth parameters. The radio signal may then be transmitted viaantenna 301 a to the appropriate recipient (e.g., UE 310).

Antenna 301 a may be any type of antenna capable of transmitting andreceiving data and/or signals wirelessly. In some embodiments, antenna301 a may comprise one or more omni-directional, sector or panelantennas operable to transmit/receive radio signals between, forexample, 2 GHz and 66 GHz. An omni-directional antenna may be used totransmit/receive radio signals in any direction, a sector antenna may beused to transmit/receive radio signals from devices within a particulararea, and a panel antenna may be a line of sight antenna used totransmit/receive radio signals in a relatively straight line.

As used herein, “user equipment” (UE) or “wireless device” (WD) refersto a device capable, configured, arranged and/or operable to communicatewirelessly with network nodes and/or another user equipment.Communicating wirelessly may involve transmitting and/or receivingwireless signals using electromagnetic signals, radio waves, infraredsignals, and/or other types of signals suitable for conveyinginformation through air. In particular embodiments, user equipments maybe configured to transmit and/or receive information without directhuman interaction. For instance, a user equipment may be designed totransmit information to a network on a predetermined schedule, whentriggered by an internal or external event, or in response to requestsfrom the network. Generally, a user equipment or wireless device mayrepresent any device capable of, configured for, arranged for, and/oroperable for wireless communication, for example radio communicationdevices. Examples of wireless devices include, but are not limited to,user equipment (UE) such as smart phones. Further examples includewireless cameras, wireless-enabled tablet computers, laptop-embeddedequipment (LEE), laptop-mounted equipment (LME), USB dongles, and/orwireless customer-premises equipment (CPE).

As one specific example, a wireless device may represent a UE configuredfor communication in accordance with one or more communication standardspromulgated by the 3^(rd) Generation Partnership Project (3GPP), such as3GPP's GSM, UMTS, LTE, and/or 5G standards. As used herein, a “userequipment” or “UE” may not necessarily have a “user” in the sense of ahuman user who owns and/or operates the relevant device. Instead, a UEmay represent a device that is intended for sale to, or operation by, ahuman user but that may not initially be associated with a specifichuman user.

The user equipment may support device-to-device (D2D) communication, forexample by implementing a 3GPP standard for sidelink communication, andmay in this case be referred to as a D2D communication device.

As yet another specific example, in an Internet of Things (TOT)scenario, a wireless device may represent a machine or other device thatperforms monitoring and/or measurements, and transmits the results ofsuch monitoring and/or measurements to another wireless device and/or anetwork node. The wireless device may in this case be amachine-to-machine (M2M) device, which may in a 3GPP context be referredto as a machine-type communication (MTC) device. As one particularexample, the wireless device may be a UE implementing the 3GPP narrowband internet of things (NB-IoT) standard. Particular examples of suchmachines or devices are sensors, metering devices such as power meters,industrial machinery, or home or personal appliances, e.g.refrigerators, televisions, personal wearables such as watches etc. Inother scenarios, a wireless device may represent a vehicle or otherequipment that is capable of monitoring and/or reporting on itsoperational status or other functions associated with its operation.

A wireless device as described above may represent the endpoint of awireless connection, in which case the device may be referred to as awireless terminal. Furthermore, a wireless device as described above maybe mobile, in which case it may also be referred to as a mobile deviceor a mobile terminal.

As depicted in FIG. 3, UE 310 may be any type of wireless endpoint,mobile station, mobile phone, wireless local loop phone, smartphone,user equipment, desktop computer, PDA, cell phone, tablet, laptop, VoIPphone or handset, which is able to wirelessly send and receive dataand/or signals to and from a network node, such as network node 300and/or other UEs. UE 310 comprises processor 312, storage 313, interface311, and antenna 311 a. Like network node 300, the components of UE 310are depicted as single boxes located within a single larger box, howeverin practice a user equipment may comprises multiple different physicalcomponents that make up a single illustrated component (e.g., storage313 may comprise multiple discrete microchips, each microchiprepresenting a portion of the total storage capacity).

Processor 312 may be a combination of one or more of a microprocessor,controller, microcontroller, central processing unit, digital signalprocessor, application specific integrated circuit, field programmablegate array, or any other suitable computing device, resource, orcombination of hardware, software and/or encoded logic operable toprovide, either alone or in combination with other UE 310 components,such as storage 313, UE 310 functionality. Such functionality mayinclude providing various wireless features discussed herein, includingany of the features or benefits disclosed herein.

Storage 313 may be any form of volatile or non-volatile memoryincluding, without limitation, persistent storage, solid state memory,remotely mounted memory, magnetic media, optical media, random accessmemory (RAM), read-only memory (ROM), removable media, or any othersuitable local or remote memory component. Storage 213 may store anysuitable data, instructions, or information, including software andencoded logic, utilized by UE 310. Storage 313 may be used to store anycalculations made by processor 312 and/or any data received viainterface 311.

Interface 311 may be used in the wireless communication of signallingand/or data between UE 310 and network node 300. For example, interface311 may perform any formatting, coding, or translating that may beneeded to allow UE 310 to send and receive data from network node 300over a wireless connection. Interface 311 may also include a radiotransmitter and/or receiver that may be coupled to or a part of antenna311 a. The radio may receive digital data that is to be sent out tonetwork node 301 via a wireless connection. The radio may convert thedigital data into a radio signal having the appropriate channel andbandwidth parameters. The radio signal may then be transmitted viaantenna 311 a to network node 300.

Antenna 311 a may be any type of antenna capable of transmitting andreceiving data and/or signals wirelessly. In some embodiments, antenna311 a may comprise one or more omni-directional, sector or panelantennas operable to transmit/receive radio signals between 2 GHz and 66GHz. For simplicity, antenna 311 a may be considered a part of interface311 to the extent that a wireless signal is being used.

Although the user equipment utilized in the example wirelesscommunication network of FIG. 2 may represent a device that includes anysuitable combination of hardware and/or software, this user equipmentmay, in particular embodiments, represent a device such as the exampleuser equipment 900 illustrated in greater detail by FIG. 4.

As shown in FIG. 4, an example user equipment 900 includes an antenna905, radio front-end circuitry 910, processing circuitry 920, and acomputer-readable storage medium 930. Antenna 905 may include one ormore antennas or antenna arrays, and is configured to send and/orreceive wireless signals, and is connected to radio front-end circuitry910. In certain alternative embodiments, user equipment 900 may notinclude antenna 905, and antenna 905 may instead be separate from userequipment 900 and be connectable to user equipment 900 through aninterface or port.

The radio front-end circuitry 910 may comprise various filters andamplifiers, is connected to antenna 905 and processing circuitry 920,and is configured to condition signals communicated between antenna 905and processing circuitry 920. In certain alternative embodiments, userequipment 900 may not include radio front-end circuitry 910, andprocessing circuitry 920 may instead be connected to antenna 905 withoutradio front-end circuitry 910.

Processing circuitry 920 may include one or more of radio frequency (RF)transceiver circuitry 921, baseband processing circuitry 922, andapplication processing circuitry 923. In some embodiments, the RFtransceiver circuitry 921, baseband processing circuitry 922, andapplication processing circuitry 923 may be on separate chipsets. Inalternative embodiments, part or all of the baseband processingcircuitry 922 and application processing circuitry 923 may be combinedinto one chipset, and the RF transceiver circuitry 921 may be on aseparate chipset. In still alternative embodiments, part or all of theRF transceiver circuitry 921 and baseband processing circuitry 922 maybe on the same chipset, and the application processing circuitry 923 maybe on a separate chipset. In yet other alternative embodiments, part orall of the RF transceiver circuitry 921, baseband processing circuitry922, and application processing circuitry 923 may be combined in thesame chipset. Processing circuitry 920 may include, for example, one ormore central processing units (CPUs), one or more microprocessors, oneor more application specific integrated circuits (ASICs), and/or one ormore field programmable gate arrays (FPGAs).

In particular embodiments, some or all of the functionality describedherein as being provided by a user equipment may be provided by theprocessing circuitry 920 executing instructions stored on acomputer-readable storage medium 930, as shown in FIG. 4. In alternativeembodiments, some or all of the functionality may be provided by theprocessing circuitry 920 without executing instructions stored on acomputer-readable medium, such as in a hard-wired manner. In any ofthose particular embodiments, whether executing instructions stored on acomputer-readable storage medium or not, the processing circuitry can besaid to be configured to perform the described functionality. Thebenefits provided by such functionality are not limited to theprocessing circuitry 920 alone or to other components of the userequipment, but are enjoyed by the user equipment as a whole, and/or byend users and the wireless network generally.

Antenna 905, radio front-end circuitry 910, and/or processing circuitry920 may be configured to perform any receiving operations describedherein as being performed by a user equipment. Any information, dataand/or signals may be received from a network equipment and/or anotheruser equipment.

The processing circuitry 920 may be configured to perform anydetermining or other operations described herein as being performed by auser equipment. Determining as performed by processing circuitry 920 mayinclude processing information obtained by the processing circuitry 920by, for example, converting the obtained information into otherinformation, comparing the obtained information or converted informationto information stored in the user equipment, and/or performing one ormore operations based on the obtained information or convertedinformation, and as a result of said processing making a determination.

Antenna 905, radio front-end circuitry 910, and/or processing circuitry920 may be configured to perform any transmitting operations describedherein as being performed by a user equipment. Any information, dataand/or signals may be transmitted to a network equipment and/or anotheruser equipment.

Computer-readable storage medium 930 is generally operable to storeinstructions, such as a computer program, software, an applicationincluding one or more of logic, rules, code, tables, etc. and/or otherinstructions capable of being executed by a processor. Examples ofcomputer-readable storage medium 930 include computer memory (forexample, Random Access Memory (RAM) or Read Only Memory (ROM)), massstorage media (for example, a hard disk), removable storage media (forexample, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or anyother volatile or non-volatile, non-transitory computer-readable and/orcomputer-executable memory devices that store information, data, and/orinstructions that may be used by processing circuitry 920. In someembodiments, processing circuitry 920 and computer-readable storagemedium 930 may be considered to be integrated.

Alternative embodiments of the user equipment 900 may include additionalcomponents beyond those shown in FIG. 4 that may be responsible forproviding certain aspects of the user equipment's functionality,including any of the functionality described herein and/or anyfunctionality necessary to support the solution described above. As justone example, user equipment 900 may include input interfaces, devicesand circuits, and output interfaces, devices and circuits. Inputinterfaces, devices, and circuits are configured to allow input ofinformation into user equipment 900, and are connected to processingcircuitry 920 to allow processing circuitry 920 to process the inputinformation. For example, input interfaces, devices, and circuits mayinclude a microphone, a proximity or other sensor, keys/buttons, a touchdisplay, one or more cameras, a USB port, or other input elements.Output interfaces, devices, and circuits are configured to allow outputof information from user equipment 900, and are connected to processingcircuitry 920 to allow processing circuitry 920 to output informationfrom user equipment 900. For example, output interfaces, devices, orcircuits may include a speaker, a display, vibrating circuitry, a USBport, a headphone interface, or other output elements. Using one or moreinput and output interfaces, devices, and circuits, user equipment 900may communicate with end users and/or the wireless network, and allowthem to benefit from the functionality described herein.

As another example, user equipment 900 may include power supplycircuitry 940. The power supply circuitry 940 may comprise powermanagement circuitry. The power supply circuitry may receive power froma power source, which may either be comprised in, or be external to,power supply circuitry 940. For example, user equipment 900 may comprisea power source in the form of a battery or battery pack which isconnected to, or integrated in, power supply circuitry 940. Other typesof power sources, such as photovoltaic devices, may also be used. As afurther example, user equipment 900 may be connectable to an externalpower source (such as an electricity outlet) via an input circuitry orinterface such as an electrical cable, whereby the external power sourcesupplies power to power supply circuitry 940.

Power supply circuitry 940 may be connected to radio front-end circuitry910, processing circuitry 920, and/or computer-readable storage medium930 and be configured to supply user equipment 900, including processingcircuitry 920, with power for performing the functionality describedherein.

User equipment 900 may also include multiple sets of processingcircuitry 920, computer-readable storage medium 930, radio circuitry910, and/or antenna 905 for different wireless technologies integratedinto user equipment 900, such as, for example, GSM, WCDMA, LTE, NR,WiFi, or Bluetooth wireless technologies. These wireless technologiesmay be integrated into the same or different chipsets and othercomponents within user equipment 900.

Abbreviation Explanation NB Narrow band NB-IoT Narrowband Internet ofThings MTC Machine Type Communications PSS Primary SynchronizationSequence SSS Secondary Synchronization Sequence SIM Module SubscriberIdentity Module or Subscriber Identification CRC Cyclic Redundancy CheckNPSS NB-IoT Primary Synchronization Sequence NSSS NB-IoT SecondarySynchronization Sequence LTE Long Term Evolution DFT Discrete FourierTransform IFFT Inverse fast fourier transform CRS Cell SpecificReference Signals PDCCH Physical Downlink Control Channel CP Cyclicprefix FDD Frequency-division duplex TDD Time-division duplex NPBCHNB-IoT Physical Broadcast Channel SNR signal to noise ratios OFDMOrthogonal frequency-division multiplexing ZC Zadoff-Chu CSS commonsearch space USS UE-specific search space PRB Physical Resource Block DLDownlink UL Uplink

1. A method performed by a user equipment (UE) in idle mode, fordetermining common search space (CSS) for Narrowband Internet of Things(NB-IoT) paging, the method comprising: determining a set of subframesas a Paging Occasion (PO) subframe pattern; monitoring a startingsubframe of the CSS for a Radio Network Temporary Identifier (RNTI);wherein the starting subframe of the CSS is determined as follows: use afirst subframe (SF0), according to the Paging Occasion subframe pattern,when the first subframe is determined to be a valid downlink subframe;and use a next valid downlink subframe after the first subframe when thefirst subframe is determined to be an invalid downlink subframe.
 2. Themethod according to claim 1, wherein the UE determines that a subframeis a valid downlink subframe if: the subframe is indicated as a validdownlink subframe in a Narrowband System Information Block 1 (NB-SIB1);and the subframe does not contain any of the following: NB-IoT PrimarySynchronization Sequence (NPSS); NB-IoT Secondary SynchronizationSequence (NSSS); NB-IoT Physical Broadcast Channel (NPBCH); and NB-SIB1.3. The method according to claim 1, wherein the Paging Occasion subframepattern is determined according to a subframe pattern table.
 4. Themethod according to claim 1, wherein the first subframe is indicated bythe Paging Occasion subframe pattern to be a starting subframe ofNarrowband Physical Data Control Channel (NPDCCH) repetitions.
 5. Themethod according to claim 4, wherein the CSS is defined only over validdownlink subframes, such that when the NPDCCH repetition overlaps withan invalid downlink subframe, the NPDCCH repetition is delayed until anext valid downlink subframe.
 6. The method according to claim 1,wherein the UE determines a subframe is a valid downlink subframe basedon a valid subframe pattern received in a System Information Block (SIB)message broadcast by a network node.
 7. The method according to claim 1,wherein the UE determines a subframe is a valid downlink subframe basedon a valid subframe pattern, the valid subframe pattern comprisingsubframes not occupied by known broadcast channels or broadcast signals.8. The method according to claim 1, wherein the UE determines a subframeis a valid downlink subframe based on a first valid subframe pattern anda second valid subframe pattern; the first valid subframe pattern beinga downlink subframe pattern received in a System Information Block (SIB)message broadcast by a network node; and the second valid subframepattern comprising subframes not occupied by known broadcast channels orbroadcast signals.
 9. A method, performed by a network node, fordetermining common search space (CSS) for Narrowband Internet of Things(NB-IoT) paging, the method comprising: determining a set of subframesas a Paging Occasion (PO) subframe pattern; transmitting a pagingmessage to a user equipment (UE), the paging message beginning with astarting subframe of the CSS; wherein the starting subframe of the CSSis determined as follows: use a first subframe (SF0), according to thePaging Occasion subframe pattern, when the first subframe is determinedto be a valid downlink subframe; and use a next valid downlink subframeafter the first subframe when the first subframe is determined to be aninvalid downlink subframe.
 10. The method according to claim 9, furthercomprising: indicating a downlink subframe as valid in a NarrowbandSystem Information Block 1 (NB-SIB1); and wherein the network nodedetermines the subframe is a valid downlink subframe if the subframedoes not contain any of the following: NB-IoT Primary SynchronizationSequence (NPSS); NB-IoT Secondary Synchronization Sequence (NSSS);NB-IoT Physical Broadcast Channel (NPBCH); and NB-SIB
 1. 11. The methodaccording to claim 9, wherein the Paging Occasion subframe pattern isdetermined according to a subframe pattern table.
 12. The methodaccording to claim 9, wherein the first subframe is indicated by thePaging Occasion subframe pattern to be a starting subframe of NarrowbandPhysical Data Control Channel (NPDCCH) repetitions.
 13. The methodaccording to claim 12, wherein the CSS is defined only over validdownlink subframes, such that when the NPDCCH repetition overlaps withan invalid downlink subframe, the NPDCCH repetition is delayed until anext valid downlink subframe.
 14. The method according to claim 9,wherein the network node transmits a valid downlink subframe pattern ina System Information Block (SIB) message broadcast to the UE.
 15. A userequipment (UE) configured for determining common search space (C SS) forNarrowband Internet of Things (NB-IoT) paging while operating in idlemode, the UE comprising: processing circuitry configured to: determine aset of subframes as a Paging Occasion (PO) subframe pattern; monitor astarting subframe of the CSS for a Radio Network Temporary Identifier(RNTI); wherein the starting subframe of the CSS is determined asfollows: use a first subframe (SF0), according to the Paging Occasionsubframe pattern, when the first subframe is determined to be a validdownlink subframe; and use a next valid downlink subframe after thefirst subframe when the first subframe is determined to be an invaliddownlink subframe.
 16. The UE according to claim 15, wherein theprocessing circuitry is configured to determine a subframe is a validdownlink subframe if: the subframe is indicated as a valid downlinksubframe in a Narrowband System Information Block 1 (NB-SIB1); and thesubframe does not contain any of the following: NB-IoT PrimarySynchronization Sequence (NPSS); NB-IoT Secondary SynchronizationSequence (NSSS); NB-IoT Physical Broadcast Channel (NPBCH); andNB-SIB
 1. 17. The UE according to claim 15, wherein the Paging Occasionsubframe pattern is determined according to a subframe pattern table.18. The UE according to claim 15, wherein the first subframe isindicated by the Paging Occasion subframe pattern to be a startingsubframe of Narrowband Physical Data Control Channel (NPDCCH)repetitions.
 19. The UE according to claim 18, wherein the CSS isdefined only over valid downlink subframes, such that when the NPDCCHrepetition overlaps with an invalid downlink subframe, the NPDCCHrepetition is delayed until a next valid downlink subframe.
 20. The UEaccording to claim 15, wherein the processing circuitry is configured todetermine a subframe is a valid downlink subframe based on a validsubframe pattern received in a System Information Block (SIB) messagebroadcast by a network node.
 21. The UE according to claim 15, whereinthe processing circuitry is configured to determine a subframe is avalid downlink subframe based on a valid subframe pattern, the validsubframe pattern comprising subframes not occupied by known broadcastchannels or broadcast signals.
 22. The UE according to claim 15, whereinthe processing circuitry is configured to determine a subframe is avalid downlink subframe based on a first valid subframe pattern and asecond valid subframe pattern; the first valid subframe pattern being adownlink subframe pattern received in a System Information Block (SIB)message broadcast by a network node; and the second valid subframepattern comprising subframes not occupied by known broadcast channels orbroadcast signals.
 23. A network node configured for determining commonsearch space (CSS) for Narrowband Internet of Things (NB-IoT) paging,the network node comprising: processing circuitry configured to:determine a set of subframes as a Paging Occasion (PO) subframe pattern;transmit a paging message to a user equipment (UE), the paging messagebeginning with a starting subframe of the CSS; wherein the startingsubframe of the CSS is determined as follows: use a first subframe(SF0), according to the Paging Occasion subframe pattern, when the firstsubframe is determined to be a valid downlink subframe; and use a nextvalid downlink subframe after the first subframe when the first subframeis determined to be an invalid downlink subframe.
 24. The network nodeaccording to claim 23, wherein the processing circuitry is furtherconfigured to: determine a subframe is a valid downlink subframe if thesubframe does not contain any of the following: NB-IoT PrimarySynchronization Sequence (NPSS); NB-IoT Secondary SynchronizationSequence (NSSS); NB-IoT Physical Broadcast Channel (NPBCH); and NB-SIB1;and indicate the subframe as a valid downlink subframe in SystemInformation Block 1 (SIB1).
 25. The network node according to claim 23,wherein the Paging Occasion subframe pattern is determined according toa subframe pattern table.
 26. The network node according to claim 23,wherein the first subframe is indicated by the Paging Occasion subframepattern to be a starting subframe of Narrowband Physical Data ControlChannel (NPDCCH) repetitions.
 27. The network node according to claim26, wherein the CSS is defined only over valid downlink subframes, suchthat when the NPDCCH repetition overlaps with an invalid downlinksubframe, the NPDCCH repetition is delayed until a next valid downlinksubframe.
 28. The network node according to claim 23, wherein theprocessing circuitry is further configured to transmit a valid subframepattern in a System Information Block (SIB) message broadcast to the UE.